In the process of producing a semiconductor device such as IC and LSI, microfabrication by lithography using a photoresist composition has been conventionally performed. Recently, the integration degree of an integrated circuit is becoming higher and formation of an ultrafine pattern in the sub-micron or quarter-micron region is required. To cope with this requirement, the exposure wavelength also tends to become shorter, for example, from g line to i line or further to KrF excimer laser light. At present, other than the excimer laser light, development of lithography using electron beam, X-ray or EUV light is proceeding.
The lithography using electron beam, X-ray or EUV light is positioned as a next-generation or next-next-generation pattern formation technique, and a high-sensitivity high-resolution resist is being demanded.
In particular, realization of high sensitivity for shortening the processing time is a very important task, but when realization of high sensitivity is sought for, not only reduction in the resolution but also worsening of the line edge roughness (LER) are caused, and development of a resist satisfying these properties at the same time is strongly demanded.
Here, the line edge roughness means that the edge at the interface between the resist pattern and the substrate irregularly fluctuates in the direction perpendicular to the line direction due to characteristics of the resist and when the pattern is viewed from right above, the edge gives an uneven appearance. This unevenness is transferred in the etching step using the resist as a mask, leading to decrease in the yield.
The high sensitivity is in a trade-off relationship with high resolution, good pattern profile and improved line edge roughness, and it is very important how satisfy all of these properties at the same time.
The resist composition includes a “positive” type using a resin sparingly soluble or insoluble in an alkali developer and forming a pattern by solubilizing the exposed area in an alkali developer by the exposure to radiation, and a “negative” type using a resin soluble in an alkali developer and forming a pattern by sparingly solubilizing or insolubilizing the exposed area in an alkali developer by the exposure to radiation.
As the resist suitable for such a lithography process using electron beam, X-ray or EUV light, in view of realization of high sensitivity, a chemical amplification positive resist composition utilizing an acid catalytic reaction is mainly studied, and a chemical amplification positive resist composition composed of, as the main component, a phenolic resin being insoluble or sparingly soluble in an alkali developer and having a property of becoming soluble in an alkali developer by the action of an acid (hereinafter, simply referred to as a “phenolic acid-decomposable resin”), and an acid generator is being effectively used.
On the other hand, the manufacture of a semiconductor device or the like requires formation of various patterns such as line, trench and hole. In order to meet the requirement for formation of various patterns, development of not only a positive resist composition but also a negative resist composition is being made (see, for example, JP-A-2002-148806 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-2008-268935).
JP-A-62-175739 discloses a resist film composed of a polymethyl methacrylate or methyl methacrylate copolymer, wherein in performing patterning by using an electron beam, development with CH3COOCnH2n+1 (n≦4) is performed in place of development with isoamyl acetate.
JP-A-2006-227174 discloses patterning utilizing a technique of cutting the polymer chain by irradiation with an electron beam and thereby reducing the molecular weight, wherein a specific organic solvent such as benzene-based solvent is used as the developer.
Japanese Patent No. 3277114 discloses a film containing a halogenated polymer or a polymer having an alkylsiloxy group as the substituent, wherein the film is exposed and then developed with a critical fluid in view of environmental problem.
JP-A-7-199467 discloses, in Examples, a positive resist film which is developed with a mixed solvent of ethyl acetate and isoamyl acetate, in place of an alkali developer.
JP-A-2010-017489 discloses a resist pattern forming method comprising, in order, a step of forming a film by using a negative chemical amplification resist composition that effects negative conversion by a crosslinking reaction, a step of exposing the film, and a step of developing the exposed film by using a developer containing an organic solvent.
However, the techniques so far are not successful in satisfying high sensitivity, high resolution, good pattern profile, reduction in the line edge roughness, and high dry etching resistance all at the same time in the ultrafine region.